Yeah it's a nice little box, but it can't play encrypted discs (i.e. commercial DVDs and whatnot). I'm still waiting for PowerDVD to integrate their HD-DVD/Blu-ray player into Vista for an all-in-one machine. I've given up hope of Apple providing this kind of HTPC solution in software (or hardware) for us. The Popcorn Hour machine look pretty good, here's the first review:

Unfortunately they got sold out very early the first day they were available, so it will be another couple weeks before the next batch is ready to order. For a discless player though, this seems like it will be the one to beat provided they live up to their advertising. My big complaint on the Tvix is that it doesn't support 1080p MKVs very well yet. Everything else played fine though, so there's nothing wrong with it other than that.

btw you were right, the GUI definitely leaves something to be desired; the Popcorn Hour machine is looking good in that department as well though!